1. Field of the Invention
The subject invention is directed to metal working operations and, in particular, to a toolholder and toolholder assembly adapted to permit a cutting insert to be secured at a non-conventional location within the toolholder.
2. Description of Related Art
During many metal working operations, it is desirable and sometimes necessary, to flush the interface between a cutting tool and the workpiece with coolant to avoid damage to the cutting tool and to the workpiece as a result of high temperatures generated at this interface and chips that may become tangled at this interface. However, depending upon the arrangement by which the cutting insert is held against the workpiece, efficient dispersion of coolant toward this interface area may be difficult, if not impossible, without significantly changing the envelope of the toolholder.
Within the metal cutting industry, the most common hardware for holding a cutting insert during a turning operation is a conventional square shank toolholder. This toolholder has a body which is typically clamped within a machine tool and the portion to be clamped has a cross-section defining four sides of equal length. The most common conventional square shank toolholder bodies have sides wherein the length is less than or equal to 1¼ inches and hereinafter reference to conventional square shank toolholder bodies will be directed to square shank toolholder bodies with the portion to be clamped having each side less than or equal to 1¼ inches. Not only is this size compact, but also permits tool access in many locations and with many machine tools that could not accommodate toolholder bodies with larger shanks. Some conventional square shank toolholders have a front end beyond the portion intended to be clamped and this front end may be larger than the portion to be clamped.
Modular toolholders permit quick insertion and/or removal of a cutting insert mounted upon a tool head. However, as a result of the internal hardware associated with modular tooling, the toolholder bodies for modular tooling must be larger than conventional square shank toolholder bodies. In particular, the minimum shank size for modular toolholder bodies is about 1½ inches. Therefore, modular toolholder bodies take up additional space and must be secured to machine tools in a different manner.
U.S. Pat. No. 6,299,388 discloses a conventional square shank toolholder with a tower extending upwardly from the toolholder through which coolant is directed downwardly upon the cutting insert. Through the introduction of such a tower, the assembly becomes significantly larger than the envelope of just the square shank toolholder and, as a result, this arrangement is not suitable for a variety of different applications in which the toolholder envelope may not exceed that of a conventional square shank toolholder.
U.S. Pat. No. 6,443,672 is directed to a cutting tool utilizing a modular toolholder, such as holder 2, which as previously discussed must be larger than conventional square shank toolholders to accommodate the additional hardware to make it operational. As a result, the width of the shank for a modular toolholder may be twice that of a comparable conventional square shank toolholder.
Typically for machines utilizing conventional square shank cutting tools, the cutting edge of cutting inserts retained in such tooling is located flush with the top surface of the square shank. For example, FIG. 1 illustrates a square shank toolholder 1 having a top surface 3 and a cutting insert 5 mounted within a pocket 7 of the square shank toolholder 1. FIG. 1 is an example of a conventional square shank toolholder with a larger front end, wherein the portion intended to be clamped is square. The insert 5 illustrated in FIG. 1 is indexable and therefore may have usable cutting edges on four sides. For purposes of discussion in this application, references to cutting edges will be to cutting edges oriented within a toolholder ready to engage a workpiece. Cutting edge 8 is one such example. The cutting edge tip 9 is positioned within the toolholder 1 so that during a metalworking operation the tip 9 is the first part of the cutting edge 8 that engages the workpiece. The active cutting edge 8 of the cutting insert 5 is positioned along a line L which overlays a line L1 extending from the top surface 3 of the toolholder 1. Aligning the cutting edge tip 9 of the cutting insert 5 with the top surface 3 of a square shank toolholder 1 is conventional practice within the industry and, as a result, if coolant must be introduced at the interface between the cutting insert 5 and the workpiece, then an arrangement such as the tower previously discussed is necessary. However, as mentioned, a tower attached to the square shank toolholder 1 will create an envelope larger than what is permissible for many applications. Furthermore, a tower on the square shank adds extra steel and overhang length to the tooling.
Modular toolholder configurations for similar operations have been designed, wherein coolant may be introduced through a wall in the pocket of the toolholder. However, these are centerline systems and, as illustrated in FIG. 2, such a toolholder 10 is secured to a flange 12, which is mounted to a machine tool (not shown). A cutting insert 15 is mounted within a pocket 17 within the toolholder 10, wherein the cutting insert 15 has a cutting edge 19. The cutting edge 19 of the cutting insert 15 is located in a plane L3 that passes through the centerline L4 of the connecting joint which, in this case, is the flange 12. The toolholder 10 has a rear wall 20 suitable to accept a bore through which coolant may be directed against the cutting insert 15. While one advantage of such a system is the interchangability of turning and boring cutting inserts for the toolholder 10 used for ID and OD machining operations, a disadvantage of this configuration is that size constraints make it impossible to fit such a centerline system into a small square shank tool envelope. Most modular toolholders require double width slots in order to be applied to a machine tool. That is, the width of the modular toolholder body is twice the width of a comparable conventional square shank toolholder body.
U.S. Pat. No. 5,718,156 is directed to a process for machining titanium parts, wherein, as illustrated in FIGS. 1 and 2 of that patent, the toolholder, which appears to have a square or rectangular shank, has a cutting insert positioned within the top surface of the toolholder to create a recess within the shank. However, a clamp (collar 2) is secured within the recess to hold the insert in place and simultaneously to direct coolant through the clamp against the cutting edge of the tip. Not only is this system fairly complex but, furthermore, the recess within the pocket must be fairly deep to accommodate the space required for the clamp.